For the first time in 20 years, Boston voters couldn’t pull the lever for Mayor Thomas M. Menino. Change was in the air.

It delivered a face-off between Marty Walsh — a state lawmaker and longtime labor leader who is the son of Irish immigrants — and John Connolly, a 40-year-old city councilor from West Roxbury, whose father is a former secretary of state and whose mother is a retired judge.

Apparently, it doesn’t take much to represent a breath of fresh air in this town.

A dozen mayoral candidates ran as change agents. The campaign trail echoed with pledges to take on the teachers’ union, untangle the permitting process, and transform stodgy old Boston into fun city. Some would-be mayors rhapsodized frequently about multiplying food trucks and smart traffic lights.

But as the field tiered, the top contenders had something in common besides their vows of change. They were younger than Menino, but they hailed from the same traditional political universe as he did. That allowed them to bring the same, old-fashioned tools of political organizing to the preliminary election. They could raise money and they could get out the vote in the neighborhoods that have long decided the outcome of Boston elections — West Roxbury, Hyde Park, and Dorchester. The difference is they had to win over neighbors in neighborhoods that are more ethnically diverse than they were in the past.

Despite his old Boston family roots, Connolly has been able to stake out the bigger claim as reformer. He got in the race before Menino got out and vowed to transform Boston public schools and bring a new transparency to Boston City Hall.

With labor money behind him, Walsh has been fighting off the label of being too union-friendly. But the teachers’ union didn’t endorse him, and a solid core of Boston progressives back his candidacy.

On the face of it, the first open mayor’s race in two decades has been left to the younger generation of Boston’s old political guard. It will be up to Walsh and Connolly to prove they stand for something new and different.